feat: Updated email templates

mail/billing.go

@@ -3,16 +3,18 @@ package mail
 // SendCancelled confirms a cancellation and states what stays true: the licence
 // keeps working until it expires, then the instance degrades to read-only.
 func (s Sender) SendCancelled(to, instanceName string) error {
-	return s.sendTemplate(to, "", "cancelled", struct {
-		InstanceName string
-	}{instanceName})
+	return s.sendTemplate(to, "", "cancelled", s.billingData(instanceName))
 }
 
 // SendPastDue notifies of a failed charge without alarming: the licence is
 // untouched while Paddle retries the card.
 func (s Sender) SendPastDue(to, instanceName string) error {
-	return s.sendTemplate(to, "", "pastdue", struct {
+	return s.sendTemplate(to, "", "pastdue", s.billingData(instanceName))
+}
+
+func (s Sender) billingData(instanceName string) any {
+	return struct {
 		InstanceName string
 		PortalURL    string
-	}{instanceName, s.PublicURL})
+	}{instanceName, s.PublicURL}
 }